Waves and Wave Interactions

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Waves and Wave Interactions

• Chapter 14 - 15
• Physical Science

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Waves

• A wave is a disturbance that carries energy
  through matter or space.
• Medium the environment that the wave travels in
  (ex water, air)

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Waves Transfer Energy

• Waves will spread out in all directions carrying
  energy.
• The energy is conserved in the system following
  both the law of conservation of momentum and
  energy.

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Waves transfer Energy

• EX Water waves do work on a boat
• EX Sound waves do work on your eardrum
• EX Light waves do work on your eye

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Energy of Waves
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Wave Speed

• The speed of a wave will depend on the medium it
  travels through
• The state of matter determines the speed of the
  wave.
• EX In gases the particles are spread out so the
  wave travels slower in gases
• EX In liquids, the particles are closer together
  so the energy is transferred quicker between
  particles of that medium
• EX In solids, the particles are tightly packed
  together so the wave travels very quickly through
  solids

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Parts of a Wave
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Doppler Effect Occurs when the wave source is
moving.

• http//www.physicslessons.com/phe/dopplereff.htm
• Image Simulation
• Breaking the sound barrier

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Light Waves

• Light waves occur in different frequencies and
  wavelengths
• Light waves are represented on the
  electromagnetic spectrum
• The Electromagnetic Spectrum consists of visible
  light and other waves that cannot be seen.

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Electromagnetic Spectrum
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Electromagnetic Spectrum
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The Electromagnetic Spectrum

• Consists of light at all possible energies,
  frequencies, and wavelengths.
• Visible light is only a small part of the
  spectrum.
• The spectrum also contains X-rays, Ultraviolet
  rays, Radio Waves, Gamma waves.

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The Nature of Light

• Light acts as a wave in that it
• produces interference patterns like water waves
• Follows the laws of reflection, diffraction, and
  refraction

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The Nature of Light

• Light also acts as a particle
• These particles are called PHOTONS
• A beam of light is considered to be a stream of
  photons.
• Photons do not have massthey are like bundles
  of energy

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Light Wave Speed

• All electromagnetic waves in empty space travel
  at the same speed
• The speed of light is 3.00 x 108 m/s or 186,000
  miles/second
• Light will travel slower when it has to pass
  through a medium such as air or water

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Wave Interference
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Wave Interference

• The combination of two or more waves of the same
  frequency that result in a single wave
• Two types
• Constructive Interference
• Destructive Interference

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Constructive Interference

• Occurs when two waves meet and produce a larger
  wave.

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Destructive Interference

• Occurs when two waves meet and make a smaller
  wave or cancel each other out.

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Wave Interference

• Interference of Light Waves produce colorful
  displays
• Ex Soap bubbles often show reds, blues, and
  yellows on their surface because of the
  interference of light.

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Wave Interference Simulation
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Wave Interactions
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Wave Interactions

• Waves may interact with each other when traveling
  through a medium
• There are 3 possible outcomes
• Reflection, Diffraction, and Refraction

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1. Diffraction

• A change in the direction of a wave when the wave
  finds an obstacle or an edge

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2. Reflection

• The bouncing back of a wave when the wave hits a
  surface or boundary

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Reflection of light

• Every object reflects some light
• Rough surfaces reflect light in many directions
• Smooth surfaces reflect light in one direction

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Law of Reflection

• When light hits a smooth surface, the angle of
  incidence equals the angle of reflection.

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3. Refraction

• The bending of waves when they pass from one
  medium to another
• Causes the wave to bend
• Prism Example
• http//www.physicslessons.com/exp33.htm

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Laws of Refraction

• When light travels in a medium with a higher
  speed to a medium where it slows down, the ray is
  bent toward the normal

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Laws of Refraction

• When light travels from a medium where it is
  slower to a medium where it can travel faster,
  light bends away from the normal

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Refraction

• Because of refraction images appear to be in
  different positions

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Wave Absorption

• Energy from the wave is absorbed into the medium
• Often as heat (measured as thermal energy).

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Thermal Energy

• Thermal conductors have a high rate of energy
  transfer
• Thermal insulators have a slow rate of thermal
  energy transfer
• Rate of thermal energy transfer is dependent on
  temperature, color, texture and exposed surface
  area of the object.

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Thermal Equilibrium

• The amount of thermal energy absorbed is equal to
  the amount of thermal energy emitted.
• The temperature remains constant.